Controllable-pitch propeller



June 27, 1939. i: CALDWELL 2,163,663

CONTROLLABLE PI TCH PROPELLER Filed June 8, 1955 2 Sheets-Sheet 1 INVENTUR WWW M; M

ATTORNEY June 27, 1939. F, w, W L 2,163,663

CONTROLLABLE -PITGH PROPELLER Filed June 8, 1935 v 2 Sheets-Sheet 2 FEW/anion L Frank M CHIdlllElf y am 4 M Aitamey Patented June 27, 1939 PATENT OFFICE CONTROLLABLE-PITCH PROPELLEB Frank W. Caldwell, Hartford, Conn., assignor to United Aircraft Corporation, East Hartford,

Conn a corporation Application June 8,

3 Claims.

This invention relates to improvements in controllable-pitch propellers and has for an object the provision of speed responsive control means for adjusting the blade angle of a controllable airplane propeller to maintain the speed of the propeller and its driving means substantially constant. A further object resides in the provision of an automatic speed responsive control for a hydraulic propeller adjusting means to adjust the blade angle or pitch of the propeller to maintain the speed of the propeller and its driving means substantially constant at a predetermined rate. Other objects and advantages will appear as the description proceeds.

In the accompanying drawings in which like numerals refer to similar parts throughout I have illustrated a suitable mechanical embodiment of what is now considered to be the preferred form of the invention. The drawings, however, is for the purpose of illustration only and is not to be taken as limiting the invention, the scope of which is to be measured entirely by the scope of the appended claims.

In the drawings, Fig. 1 is a partly schematic view showing a propeller controlling device constructed according to the idea of this invention. certain portions being shown in section to better illustrate the construction thereof. Fig. 2 is a view similar to Fig. 1 showing the propeller control mechanism in a 'difierent operative position from that illustrated in Fig. 1. Fig. 3 is a longitudinal sectional view on a somewhat enlarged scale of a suitable propeller pitch changing mechanism.

Referring to the drawings in detail, the numeral l0 generally indicates a propeller driving means which may be a radial internal combustion engine of the type commonly employed for the propulsion of airplanes. The engine it projects a rotatable power shaft M, the outer end of which is drivingly connected to a propeller generally indicated at MS. The propeller may be of any suitable type such as that shown in Patent No. 2,032,254. The propeller blades as indicated at 20 are rotatable about their longitudinal axes to adjust the pitch or angle of attack of the blade to the air through which the propeller moves to vary the load imposed by the propeller upon the engine In. The blades 2|] are automatically urged to rotate in a direction to increase the blade angle by centrifugal members as indicated at 22, one centrifugal member being rigidly attached to each propeller blade adjacent to its root or hub end. As the propeller rotates,

is provided with a crankcase 12 from which of Delaware 1935, Serial No. 25,615

the action of centrifugal force upon the centrifugal members 22 tends to swing these members outwardly from the axis of rotation of the propeller in a direction to rotate the propeller blades to increase the blade angle as stated. The propeller blades are urged to rotate in a direction to decrease the blade angle and thus decrease the load on'the engine ill by means of a hydraulic device comprising, a piston 24 and a cylinder 26 reciprocably mounted upon the piston and operatively connected to the propeller blades by suitable means such as the links indicated at 28. An outward movement of the cylinder 26 with respect to the piston 24 tends to rotate the blades 20 against'the action of the centrifugal members 22 in a direction to decrease the blade angle of the propeller. Outward movement of the cylinder 26 with respect to the piston 24 is obtained by injection of a fluid under pressure into the space between the interior of the cylinder and the outer end of the piston. This fluid under pressure may be obtained from any suitable source such as the oil pump 35 on the engine in and may be led to the propeller through suitable conduits as indicated at 32 and 34, the conduit 34 hereinafter referred to as the propeller line being connected through an oil collector ring 35 with a bore 38 extending through the drive shaft M to the interior of the cylinder 26.

The flow of pressure fluid to the cylinder 26 is controlled by a speed governor generally indicated at 40 and a servo valve generally indicated at 42. The governor fill is driven from the engine ill by means of a suitable connection 44, attached at one end to a rotating part of the engine as indicated at 46. Obviously, the governor will be driven at engine speed or at any fraction or multiple thereof depending upon the speed of rotation of the element 6 to which the connection 44 is attached. The governor illustrated is of the flyball type and is operatively connected to a pilot valve generallyindicated at 48 by means of a valve stem 50 to which is secured a thrust plate 52 against which the flyballs 54 react as they move radially outward under the influence of centrifugal force. The free end of the valve stem 50 is rigidly connected to a piston 56 which reciprocates in a cylinder 58 under the influence of the governor, the piston being biased in one direction by a coiled compression spring 60 interposed between the piston and the adjacent end of the cylinder 58 and acting in a direction to urge the flyballs 54 of the governor 40 inwardly against the action of centrifugal force. One side of the cylinder 58 is connected to the engine oil sump 62 by a conduit 64 having leads 65 and 61 at the opposite ends of the cylinder and the opposite side of this cylinder is hydraulically connected to the cylinder 66 of the servo valve 42 by two parallel conduits as indicated at 68'and 18, the ports by which the leads 65 and 61 and the conduits 68 and 18 are connected to the cylinder 58, being so arranged that in one operative position of the pilot valve piston 56, as illustrated in Fig. 1, the piston obstructs the conduit 68 while at the same time permitting the conduit I0 to be connected with the drain line 64 and in the other operative position of the piston 56, as illustrated in Fig. 2, the piston obstructs the conduit 18 while permitting the conduit 68 to be connected with the drain line 64. The piston 56 has a length such that it covers both of the ports of the conduits 68 and 18 when in a position intermediate the extreme position illustrated. The cylinder 66 of the servo valve is in efiect a double cylinder and is divided into two separate chambers by means of a partition 'or diaphragm 12. A valve stem 14 projects through the partition 12 and carries on one side of the partition a valve operating piston 16 and upon the opposite side of the partition a pair of hydraulic control pistons 18 and 88. The conduits 66 and 18 leading from the pilot valve 48 are connected to the chamber portion of the cylinder 66 containing the piston 16, the ports connecting these conduits with the interior of'the chamber being disposed adjacent to the opposite ends of the chamber, and the pressure line 32 from the oil pump 38 has two leads, as indicated at 82 and 84, which are led into the chamber containing the piston 16 through restricted ports disposed substantially opposite the ports of the conduits 68 and 18 respectively.

From the above description it will be observed that when the piston 56 of the pilot valve 48 is in the position illustrated in Fig. 1 in which it blocks the conduit 68 and permits the conduit 18 to be connected with the drain 64, the chamber space on that side of the piston 16 adjacent to the conduit 18 will be drained as the fluid cannot flow into the chamber through the restricted port in conduit 84 as rapidly as it flows out through conduit I8, and fluid under pressure will flow into the chamber on that side of the piston 16 adjacent to the blocked line 68 thus causing the piston 16 to move downwardly as illustrated in Fig. 1. When the pilot valve piston 56 is in the position illustrated in Fig. 2, blocking the conduit 18 and permitting the conduit 68 to be connected with the drain 64, pressure will build up under the piston 16 and decrease above the piston because of the restricted port in conduit 82 so that the piston will be moved upwardly as illustrated in Fig. 2. It will thus be seen that the action of the governor 48 in response to the speed of the engine l8 as transmitted to the governor through the drive 44 and through the medium of the pilot .valve 48 actuates the servo valve 42 from one to the other of its two operative positions. The chamber of the servo valve 42 containing the pistons 18 and 88 has connected to one side thereof, the drain line 64 through ports disposed adjacent to the opposite ends of the chamber. The pressure line 32 is also connected to the chamber containing the pistons 18 and 88 through a port disposed substantially centrally of the chamber as indicated at 86.. The propeller line 34 is also connected to this chamber through a port 88 adjacent to the port 86. When the servo valve is in the operative position illustrated in Fig. 1, it will be observed'that the piston 18 blocks the port 86 of the pressure line 32 and the propeller line 34 is connected with the drain line 64 through the space between the pistons 88 and 18, in this position of the servo valve, the pressure fluid is drained from the cylinder 26 and returned through the conduit 34, the servo valve 42 and the drain line 64 to the engine sump 62 speed up. In the position of the parts as illustrated, the flyballs 54 of the governor 48 have been moved inwardly by the spring 68 under reduced centrifugal force and, at the same time the piston 56 of the pilot valve has been moved downwardly to uncover the port of the conduit 68, to allow this conduit to drain, and to block the port of the conduit 18. This action of the pilot valve will cause the pressure above the piston 16 of the servo valve to decrease and the pressure be-' low piston 16 to increase thus moving the piston upward to the position illustrated in Fig. 2. As the piston 16 is rigidly connected to the pistons 18 and 88 of the servo valve these pistons are moved upwardly so that the piston 18 is out of blocking relation with the port 86 thus connecting the pressure line 32 with the space between the pistons 18 and 88. The piston)", however, has also moved upwardly and in the position illustrated in Fig. 2 blocks thedrain'line 64 and permits the pressure line to be connected with the propeller line 34, thus supplying fluid under pressure to the cylinder 26 to adjust the propeller to a low pitch condition as stated above.

From the above description it will be observed that I have provided an automatically controlled hydraulic means for adjusting the blade angle of a controllable propeller in response to the speed of the propeller driving means to vary the load placed upon the driving means by the propeller and thereby maintaining the speed of the driving means substantially constant.

While I have illustrated and described a particular mechanical embodiment of the idea of my invention, it is to be understood that the insuch changes in the size, shape, and arrangement of parts may be resorted to as come within the scope of the sub-joined claims.

Having now described my invention so that others skilled in the art may clearly understand the same, what I desire to secure by Letters Patent is as follows. 1

What I claim is:

1. In combination with a controllable propeller and driving means therefor, means for automatically adjusting the blade angle of said propeller, a pressure line, a drain, and means for connecting said propeller adjusting means with said pressure line or said drain comprising, a servo valve having two chambers, a piston in each chamber said pistons being operatively connected together, means hydraulically connecting said propeller adjusting means, said pressure line and said drain to one of said chambers, means con-,-

the other of said chambers, a pilot valve, means connecting said pilot valve with said drain, means comprising a pair of spaced conduits connecting said pilot valve with said other chamber, and a speed responsive mechanism for operating said pilot valve.

2. In combination with a controllable propeller and driving means therefor, means for automatically increasing the blade angle of said propeller upon rotation of said propeller by said driving means, a piston, a cylinder reciprocally mounted upon said piston and operatively connected to said propeller to decrease the blade angle of said propeller upon the injection of fluid under pressure into the space between said piston and said cylinder, a pressure line connected with the space between said piston and said cylinder, a drain, a servo valve operative to connect the space between said piston and said cylinder with said pressure line or said drain, hydraulic means including a cylinder and a piston reciprocable in said cylinder for operating said servo valve, a pilot valve for controlling said hydraulic means and a governor driven bysaid propeller driving means and operatively connected with said pilot valve to actuate said pilot valve to control said servo valve in response to speed changes in said propeller driving means.

3. In combination with a controllable propeller and driving means therefor, centrifugal means secured to said propellerfor automatically increasing the blade angle of said propeller upon rotation of said propeller by said driving means, a piston, a cylinder reciprocally mounted upon said piston and operatively connected to said propeller to decrease the blade angle of said propeller upon the injection of fluid under pressure into the space between said piston and said cylinder, a pressure line connected with the space between said piston and said cylinder, a drain, a servo valve operative to connect'the space between said piston and said cylinder with said pressure line or said drain, hydraulic means including a cylinder and a piston reciprocable in said cylinder for operating said servo valve, a pilot valve for controlling said hydraulic means and a governor driven by said propeller driving means and operatively connected with said pilot valve to actuate said pilot valve to control said servo valve in response to speed changes of said propeller driving means.

FRANK W. CALDWELL. 

